This article introduces a special issue on the micro-level dynamics of mass violent conflict. While most analyses of conflict typically adopt a regional, national or global perspective, often using country-level data, this special issue takes an explicit micro-level approach, focusing on the behaviour and welfare of individuals, households and groups or communities. At a fundamental level, conflict originates from individuals' behaviour and their repeated interactions with their surroundings, in other words, from its micro-foundations. A micro-level approach advances our understanding of conflict by its ability to account for individual and group heterogeneity within one country or one conflict. The contributors to this special issue investigate the nature of violence against civilians, the agency of civilians during conflict, the strategic interaction between civilians and armed actors, the consequences of displacement, the effectiveness of coping strategies and the impact of policy interventions. The core message from these articles is that in order to understand conflict dynamics and its effects on society, we have to take seriously the incentives and constraints shaping the interaction between the civilian population and the armed actors. The kind of interaction that develops, as well as the resulting conflict dynamics, depend on the type of conflict, the type of armed actors and the characteristics of the civilian population and its institutions.